1. Field of the Invention
The present invention relates to an apparatus and method for performing a drilling operation within the interior of a well or the like and, in particular, to such an apparatus and method wherein means are provided for advancing a drill bit or tool to engage the wall or casing of the well and to withdraw the tool after completion of the drilling operation.
2. Description of the Prior Art
It is not uncommon during the life of a water, oil or gas well for the perforations in the well casing through which fluid passes to become clogged or, in the case of a water well, for the water table to drop significantly, such that new perforations must be made or the old perforations relocated.
In the past, this has been accomplished in any of several ways. In the case where the water table has dropped, one such way is to use an apparatus which drives or pounds the well casing deeper into the earth so that the perforations are again below the water table. However, the driving of the casing requires the use of expensive and large equipment and will sometimes cause the well casing to collapse.
If new perforations are desired, a scissor-type tool may be lowered into the casing which will slit the sides of the casing to create new openings. It is also know to use a gun-type perforator which is lowered into the casing and which shoots projectiles into the casing to create perforations. These types of operations will frequently weaken or seriously damage the well casing.
It has also been proposed to lower a drilling mechanism into a well casing to drill new perforations. An example of such a drilling mechanism is shown in U.S. Pat. No. 3,528,515, entitled "Rotary Perforating Tool and System for Well Perforation," issued to M. A. Garrison. The problem with a drilling mechanism is that there is required a device for remotely advancing and withdrawing the drill member or bit, and this often makes the drilling mechanism expensive, because of the numerous mechanical components involved, and difficult to support within the well casing during operation. In addition, failure of the mechanical components of the mechanism before withdrawal of the drill bit from the perforation can result in the drill bit being lodged in the casing and can require that the mechanism be dismantled piece by piece within the casing, or even that it be abandoned within the casing and a new well dug.